Conduction-responsive meter head

Abstract

A conduction-responsive meter head has a device having electrical conduction responsive to a condition such as pressure to be metered. The device communicates with the condition to provide its electrical-conduction response to a bridge electrically including the device. A power supply has two terminals on the meter head for providing electrical power to the bridge. The measurement signal from the bridge is provided, however, to a third terminal by a lead from the bridge.

What is claimed is: 
     
       1. A conduction-responsive meter head, comprising: a device having electrical conduction responsive to a condition to be metered and means for communication with the condition, whereby to provide such electrical-conduction response;   a bridge electrically including the device;   power supply means comprising two terminals for providing electrical power to the bridge;   measurement signal comprising a third terminal and a lead connecting the third terminal to the bridge for providing a measurement signal from the bridge to the third terminal; and   a current transformer series-inserted in the lead.   
     
     
       2. The meter head of claim 1, and further comprising an amplifier series-inserted in the lead for varying the measurement signal provided thereby from the bridge to the third terminal in a characteristic way. 
     
     
       3. A conduction-responsive meter head, comprising: a device having electrical conduction responsive to a condition to be metered and means for communication with the condition, whereby to provide such electrical-conduction response;   a bridge electrically including the device;   power supply means comprising two terminals for providing electrical power to the bridge;   measurement signal means comprising a third terminal and a lead connecting the third terminal to the bridge for providing a measurement signal from the bridge to the third terminal;   a balancing resistor in the bridge and a balancing resistor series-inserted in the lead; and   a current transformer series-inserted in the lead.   
     
     
       4. The meter head of claim 3, and further comprising an amplifier series-inserted in the lead for varying the measurement signal provided thereby from the bridge to the third terminal in a characteristic way. 
     
     
       5. A conduction-responsive meter head, comprising: a device having electrical conduction responsive to a condition to be metered and means for communication with the condition, whereby to provide such electrical-conduction response;   a bridge electrically including the device;   power supply means comprising two terminals for providing electrical power to the bridge;   measurement signal means comprising a third terminal and a lead connecting the third terminal to the bridge for providing a measurement signal from the bridge to the third terminal; and   a second device having electrical conduction responsive to the condition to be metered and means for communication with the condition, whereby to provide such electrical-conduction response; and a second bridge electrically including the second device; and   the power supply means being also for providing electrical power to the second bridge; and   the lead of the measurement signal means also connecting the third terminal to the second bridge for providing a combined measurement signal from both of the bridges to the third terminal.   
     
     
       6. The meter head of claim 5, wherein one device is a temperature-dependent resistor and the other device is a piezo-relative device. 
     
     
       7. A conduction-responsive meter head, comprising: a device having electrical conduction responsive to a condition to be metered and means for communication with the condition, whereby to provide such electrical-conduction response;   a bridge electrically including the device;   power supply means comprising two terminals for providing electrical power to the bridge;   measurement signal means comprising a third terminal and a lead connecting the third terminal to the bridge for providing a measurement signal from the bridge to the third terminal; and   two further terminals and a variable resistor connected across the terminals for equalizing a display of the measurement signal when the display is connected to the terminals.